I've tinkered with a bit of high speed photography (catching a water drop with low power flash in a dark room) and had success, but mostly through the volume of trials.
I've got a shot in mind (I'd like to drop an Oreo into a glass of milk), and I'd like to minimize the number of tries it takes to work.

What techniques are there to help capture such shots?

UPDATE: Regarding the answers below, they touch on how to do high speed photography, but I was really hoping for a detailed technique for triggering the flash that was more than luck and at least more detailed than a link elsewhere. I may be hoping for too much, time will tell.

I've used my water drop technique for this as well, it just takes a lot more luck to get a good shot and it takes some good hand-eye coordination to drop and trigger. I suspect, however, that there are easier ways to do it without resorting to laser triggers, etc.
– John CavanJan 27 '11 at 20:52

3 Answers
3

Because I am sometimes asked to do these sorts of shots as part of my business, where 'trial and error' is often incompatible with 'client budget,' I use a programmable intervalometer with a variety of sensors which give me that ability to capture the sorts of pictures where 'timing is everything.' Among other things over the years I've used such devices to capture images of bullets being fired, arrows flying, explosions, water drops, things being dropped into various types of liquid, 'shy' animals, and to 'slow down' industrial machines.

Although I've used many different systems, currently I use the Mumford Time Machine, and I've been very pleased with it.

While I realize that my answer may not appeal to everyone (DIYers, hobbyists, etc.), for someone with more money than time, or who is capturing these sorts of images professionally and doesn't have time to do it '600 times and pray one of them is usable,' there are definitely pro-level options that don't involve 'picking up a soldering iron.'

Trigger the flash (low power flash for a very fast burst) at the correct time.

Flash can be triggered by sound ( useful if you want to take a broken glass picture) or laser sensor ( useful for moving objects ). Sometimes a small delay should be added. Often an Arduino board is used to control the electronics as described here or here for instance.

That "Trigger the flash at the correct time." is the kicker.
– rfuscaJan 27 '11 at 19:29

Noob question probably but why do you need a flash, rather than a constant light source such as a spotlight?
– Winston SmithJan 27 '11 at 19:50

5

@Winston Smith - A low power flash burst is so fast, that the picture is only really exposed for an incredibly brief period of time (often much shorter than any shutter speed, like 1/30000th of a second) that the light "freezes" the action.
– rfuscaJan 27 '11 at 19:57

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@Winston: because a speedlight-style flash, especially at low power, emits a very brief pulse of light which can freeze motion much more effectively than the shutter.
– mattdmJan 27 '11 at 19:57

For shooting an Oreo in milk you don't necessarily need a very high speed. In the image below you can see similar idea where the speed was 1/250sec (flash sync speed):

In the past I tried capturing waterdrops. The problem was that with my older 380ex flash, when it was set off-camera it fired in full power, so the exposure was too long to get a real sharp, frozen drop. So my advice is to use a flash in manual mode, set to a low power so the exposure is as short as possible. Alternatively, you can use high-speed sync mode, if you can control your off-camera flash in this manner (unfortunately, the flash master in the EOS 7D does not allow for HSS when controlling the 580EXII using the built-in flash).

Still for the Oreo shot, use a wireless trigger to trigger the camera while releasing the cookie into the milk. It took me a surprisingly small amount of trials to get to a good timing with the lemon splash.

If you feel inspired, you can build yourself a IR beam detector trigger that will trigger the camera once the cookie crosses the beam. UPDATE: HiViz is a good resource for HS photograhy.

Keep in mind if you're using a flash and you keep the ambient light low (relative to your exposure), the flash strobe speed is what is freezing your subject, not your shutter. The shutter could be 1/15s but your flash is somewhere around 1/20,000s and thats what matters.
– ShizamJan 27 '11 at 22:58

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HSS is the opposite because it strops the flash multiple very, very rapidly times in order to simulate a longer-duration (effectively continuous) light source. That's what I mean by "the opposite" of freezing motion.
– mattdmJan 28 '11 at 0:24

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@mattdm - I see what you mean, but on the other hand, it is what let you use shutter speeds faster than 1/250. See the couple of comments above.
– ysapJan 28 '11 at 0:27

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And, I still don't think it's an equivalent result — manual power gives you more light and the possibility of much shorter durations. That gives you more flexibility — more control over the process. Plus, since the cutoff is electronic rather than actual physical motion, I suspect that the variation shot-to-shot is much smaller, allowing more consistently-repeatable results (but I have no reference to back this up).
– mattdmJan 28 '11 at 5:27